This invention is in th e field of Signature Verification. The invention is more particularly directed towards a method of determining whether or not an individual signing his name is the same individual who signed the same name which was provided as a reference signature by this individual. According to this invention the movement of the writing instrument as the name is signed is used to provide a series of data points represents of that person's signature.
Related applications which describe a method of reading typed text which are commonly assigned and are hereby incorporated by reference are as follows. Ser. No. 115,986, filed Jan. 28, 1980, Inventor, Warner C. Scott; Inventor Warner C. Scott; Ser. No. 153,342, filed May 27, 1980, Inventor, Warner C. Scott; Ser. No. 501,037, filed June 1, 1983, Inventor, Warner C. Scott; Ser. No. 527,152, filed Aug. 26, 1983, Inventor, Warner C. Scott; Ser. No. 527,702, filed Aug. 26, 1983, Inventors, Warner C. Scott, Keith A. Blanton, Steven Petersen and Ramon Helms; Ser. No. 527,151, filed Aug. 26, 1983, Inventors, Steven Petersen, Keith Blanton and Ramon Helms; Ser. No. 527,155, filed Aug. 26, 1983, Inventors Keith Blanton, Steven Petersen and Ramon Helms; Ser. No. 527,731, filed Aug. 26 1983, Inventors, Keith Blanton, Steven Petersen and Ramon Helms; Ser. No. 527,150, filed Aug. 26, 1983, Inventors, Steven Petersen, Keith Blanton and Ramon Helms; Ser. No. 546,782, filed Oct. 27, 1983, inventor, Warner C. Scott; Ser. No. 546,752, filed Oct. 27, 1983, C. Scott filed concurrently herewith.
It is desirable for a different application to verify that an individual signing a particular name is in fact the individual whose name he is signing. One method of determining whether or not the identity of the person matches the name he has signed is the use of signature verification. According to this invention an individual provides a reference signature by signing his name a plurality of times to enroll his signature. A signature selected from those provided is a reference signature representative of that persons signature when they sign their own name. At a later point in time when an individual purports to be the same individual who provided the reference signature that individual is required to replicate the reference signature. This replication is known as the sample or data signature and provides a series of data points for comparison with a reference signature which it purports to match. The sample signature and reference signature are compared with each other and an indication is given whether or not the same individual signed both of the signatures.
This invention would find use in the banking industry, where a person could simply sign his name to indicate his identity and the signature of the name alone would be sufficient verification of identity to allow the bank to dispense funds. This could be done through an automatic teller machine or other device, thus saving considerable funds in hiring extra tellers to provide this service. Additionally, this could find use in many other applications, such as, access to particular locations, use of credit cards, or other times when the identity of the individual signing the name must be verified.
This invention uses unique factors and a combination of unique factors to determine whether or not handwritten signatures belong to the same individual. The approach of this invention is to gather data as the text is written. In this embodiment the writing is performed on a data tablet which records the location of the pen at a point in time on the clock pulse. The data tablet provides the X and Y coordinate of the pen at the point in time that the data is sampled. The X and Y coordinate of each data point is used to produce a one-dimensional waveform of the character as it was written. The waveform of the character has as the abscissa the path length of the pen and as the ordinate the direction of movement. This one-dimensional array of the data is an important beginning to a simplification of an individual's signature. It is important to note that the abscissa of the plot as shown in the accompanying figures is path length and not time. This means that individual handwriting speed, writing part of the letter faster than another part and other variations thereon do not affect performance in any way.
The X-Y data tablet indicates the location of the writing instrument at a predetermined clock pulse rate as the signature is written. A number string is generated which indicates the relationship between sequentially determined locations of the writing instrument as it moves to different locations on the X-Y data tablet. The quantity of numbers within the number string is an indication of the distance between sequentially determined locations and the value of the numbers within the number string is an indication of the direction of movement between sequentially determined locations. Series of number strings form a waveform representative of the signature as written by the individual. The waveform of the sample signature is compared with the waveform of a reference signature and an output is provided indicating whether or not the sample signature and the reference signature were made by the same individual. The two waveforms are compared to each other by size normalizing the waveforms, aligning the buoys of the waveforms with each other, determining the integral of the difference between the waveforms for various buoy alignments and providing an integral of the difference of the waveforms for their entire length. The integral is then divided by the number of data points within the signature so that an average difference between the two waveforms is provided. The average difference between the two waveforms provides an indication whether or not the same individual signed both signatures.
Signatures can be compared both qualitatively and quantitatively to determine the degree of match between the signatures. A person or handwriting expert reading the text may perform qualitative analysis and look for similarities in a qualitative manner. However, it is difficult for a computer to perform qualitative analysis. One object and advantage of this invention is the placing of handwritten signatures having numerous qualitative features into a quantitative form. This in effect quantitizes the numerous qualitative features. The quantitative form may then be analyzed by a computer and a quantitative output of the computer or microprocessor takes into account numerous qualitative features which is achieved through use of the waveforms and various comparison techniques.
The applicant has also provided a way of placing a handwritten signature in polar coordinates having length and direction, (r, .theta.), to describe the movement of the pen in a sequence the ignature is written. The use of polar coordinates and having the magnitude of the polar coordinate being the abcissa and the direction the ordinate is most useful in this invention and is one of the steps of this invention which permits quantitative comparison of qualitative data. This effectively produces a continous history of pen movement as indicated by polar coordinates. The direction of the polar coordinate, .theta., is determined as the direction of movement from on equential point to another on the X-Y data tablet. The magnitude, r, is determined as the distance of one location to the next. In the embodiment described herein the polar coordinates are determined using an X-Y data tablet in conjunction with a look-up table as stored in the microprocessor memory. The polar coordinates could also be determined using numerous other techniques. It can be seen looking at FIGS. 4 and 5 that .theta. is determined from FIG. 5 and r is determined from FIG. 4 to make up the polar coordinate for each point of the waveform. The polar coordinate could be separately determined using different techniques if desired. This method of reducing handwritten signatures to data for comparison with other handwritten signatures is to be contrasted with numerous other techniques as a sequential continuous history of movement of the writing instrument.
Numerous other novel features of this invention are also used in combination with the waveform to produce a novel technique of quantitatively analyzing a handwritten signature.
An apparatus for carrying out this invention can be provided with a relatively inexpensive X-Y data tablet and a microprocessor chip with an appropriate output and memory. This is an extremely inexpensive implementation and yet is used in such a manner as to permit signature verification of many individuals.
It is an object of this invention to provide a method of verifying whether or not the same individual has signed two signatures which are provided.
It is a further object of this invention to provide a method of implementing a signature verification apparatus which is relatively inexpensive.
It is a further method of this invention to implement a signature verification method which is extremely quick and accurate.
It is a further object of this invention to provide data representative of an individual signature which is a one-dimensional array without time being a factor within the array.